SCOSTEP/PRESTO Online Seminar Series

In collaboration with the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) under the International Science Council (ISC), ISEE/CICR has operated SCOSTEP/PRESTO Online Seminar Series as below. The recordings of these online seminars are available from here.

SCOSTEP Distinguished Scientist Award 2024 Ceremony
and the 25th SCOSTEP/PRESTO Online Seminar

Speaker: Dr. Jie Zhang, Department of Physics and Astronomy, George Mason University, Virginia, USA
Date and Time: November 8, 2024 (Fri), 15:00-16:00 UT (10:00-11:00 EST)
Title: "Solar Eruptions: Initiation, Propagation and Their Earth Impact"
Link to the video

Abstract: Flares and coronal mass ejections (CMEs) are the two largest energetic phenomena originating in the Sun’s atmosphere. They are different in observations: flares are manifested as a spontaneous release of EM radiations in almost all wavelengths through the acceleration of non-thermal particles and plasma heating, while CMEs, equally energetic, are observed as the eruption and ejection of a large-scale organized magnetic structure into the outer corona. In this talk, I will first reflect on the debate in the 1990s on the so-called “solar flare myth”, which initiated the paradigm shift on the cause of space weather from a flare-centered view to a CME-centered view. Secondly, a comprehensive overview of our improved understanding of the relationship between flares and CMEs will be made. Thanks to the advancement in observations made by a series of modern space observatories, including SOHO, STEREO and SDO, it has been found that mostly the energetic process of a flare (e.g., the increase of X-ray flux) and the accompanying CME (e.g., the increase of the CME velocity) is highly synchronized in time. They are intimately coupled in the energy release process; thus, they should be collectively called a solar eruption. On the other hand, the Sun shows a zoology of the phenomena, as they can also occur independently from each other, namely confined flares and “stealthy” CMEs, respectively. The physical causes of the coupling and the diversity will be discussed in this talk. Lastly, how and what solar eruptions affect the geo-space, i.e., the Sun-to-Earth chain activities, will be presented, with a focus on the in-situ solar wind properties from two types of CMEs, i.e., originated from active regions versus those from quiescent regions.

24th SCOSTEP/PRESTO Online Seminar

Speaker: Dr. Manuela Temmer, Institute of Physics, University of Graz, Austria
Date and Time: October 9, 2024 (Wed), 11:00-12:00 UT (13:00-14:00 CEST)
Title: "Structure and dynamics of the heliosphere – a better understanding for better Space Weather forecasting"
Link to the video

Abstract: The Sun's most energetic phenomena are coronal mass ejections (CMEs) and solar flares. CMEs are massive clouds of magnetized plasma that can travel at speeds of several thousand kilometers per second, capable of crossing the Sun-Earth distance in less than one day. When they reach Earth, they can cause significant geomagnetic disturbances, collectively known as Space Weather. CMEs move through the ambient solar wind, a flow shaped by the interaction between slow and fast wind streams. These streams create stream interaction regions (SIRs), which can trigger geomagnetic storms themselves, often in a recurring pattern. The recent surge in solar activity, highlighted by the intense "May 2024" solar storms, has heightened even more the interest in understanding the origin and effects of dynamic solar wind structures on Geospace. To improve the accuracy of space weather forecasts, it's essential to understand the physical processes that govern the interaction between CMEs and the solar wind. This seminar will focus on eruptive CME-flare events, the interplanetary propagation behavior of CMEs and their relation to the background solar wind.

SCOSTEP Distinguished Young Scientist Award 2024 Ceremony
and 23rd SCOSTEP/PRESTO Online Seminar

Speaker: Dr. Man Hua, Department of Atmospheric and Oceanic Sciences, UCLA, Los Angeles, USA
Date and Time: September 23, 2024 (Mon), 22:00-23:00 UT (15:00-16:00 PDT)
Title: "Upper Limit of Earth’s Outer Radiation Belt Electron Fluxes: How Intense Can It Get and Why?"
Link to the video

Abstract: The Earth’s outer radiation belt is populated by highly energetic electrons (hundreds of keV to multi-MeV), also known as “killer” electrons due to their deleterious effects on satellites. These electrons can be quickly accelerated with fluxes varying up to several orders of magnitude, primarily due to local acceleration by whistler-mode chorus waves and/or inward radial diffusion. Historically, these electron dynamics have been associated with geomagnetic storms. However, it remains unclear what is the critical geomagnetic condition that governs the electron acceleration during both storm and non/weak storm time. Additionally, the question of how intense radiation belt electron fluxes can get and why there is an upper limit—a question first raised in 1966—remains a mystery. This seminar will present recent findings aimed at addressing this question, where we seek to understand the underlying physical mechanisms and the critical geomagnetic conditions that control the upper limit of outer belt electron fluxes, by using both numerical simulations and statistical analysis of satellite observations. Our results reveal, for the first time, the natural upper limit of electron acceleration by chorus waves, which explains the observed energy-dependent maximum fluxes that were close to the highest upper limit during the Van Allen Probes Era. Furthermore, our statistical analysis identifies a strong correlation between the time-integrated substorm index (Int(AL)) and upper limit of electron fluxes, demonstrating the significant impact of the cumulative substorms on electron dynamics. While intense storms can provide favorable conditions for efficient acceleration, they are not necessarily required to produce large maximum fluxes.

22nd SCOSTEP/PRESTO Online Seminar

Speaker: Dr. Nat Gopalswamy, Heliosphysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
Date and Time: July 30, 2024 (Tue), 13:00-14:00 UT (09:00-10:00 EDT)
Title: "Space Weather Consequences of a Weak Heliospheric State"
Link to the video

Abstract: Coronal mass ejections (CMEs) have been established as the primary source of severe space weather in terms of major geomagnetic storms and large solar energetic particle (SEP) events. Such CMEs generally have a large angular width and high speed, indicating that they are very energetic. While exploring the reasons for mild space weather in solar cycle 24, it was found that the speed-width relationship has a larger slope in this cycle than in cycle 23. In other words, for a given speed, cycle 24 CMEs are wider than the cycle-23 ones. Halo CMEs constitute a special population of CMEs that are wide enough to appear above the occulting disk at all position angles in sky-plane projection. Halo CMEs also behaved differently in cycle 24: their occurrence rate did not decrease commensurate with the reduction in the Sunspot Number (SSN) relative to cycle23. It was concluded that the weak state of the heliosphere (indicated by a lower heliospheric total pressure measured at 1 au) due to relatively weak solar activity in cycle 24 backreacted on CMEs to make them appear wider. Such a backreaction can explain both the changed speed-width relationship and higher halo CME abundance in cycle 24. These conclusions have been shown to hold good in cycle 25, which is currently in its maximum phase. Furthermore, the heliospheric state in cycle 25 is similar to that of cycle 24 indicating that these two cycles have similar strength. The backreaction of the weak heliospheric state on CMEs resulted in a significant reduction in the number of high-energy SEP evets and intense geomagnetic storms. This seminar focuses on the complex connection among the CME properties, the heliospheric state, and the space weather consequences.

21st SCOSTEP/PRESTO Online Seminar

Speaker: Dr. Hanli Liu, High Altitude Observatory, NCAR, USA
Date and Time: April 29, 2024, 23:00-24:00 UT (18:00-19:00 EST)
Title: "It's YES for NO, O/N2 and e: Perturbative and transport effects by gravity waves in the mesosphere, thermosphere and ionosphere"
Link to the video



Abstract: WACCM-X (Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension) shows significance biases in representing several key constituents in the middle and upper atmosphere, including nitric oxide (NO) in the mesosphere and lower thermosphere (MLT), the O/N2 in the thermosphere, and the plasma density in the ionosphere F-region. These biases are thought to be related to transport, though the exact causes are not well understood. Moreover, perturbative effects of the gravity waves are not accounted for in current parameterization schemes, but they are known to be important for processes in the middle and upper atmosphere, for example temperature dependent chemical reactions, traveling atmospheric/ionospheric disturbances (TADs/TIDs), and ionospheric irregularities. These challenges motivate the development of the high-resolution (HR) capability of WACCM-X, and in this study we examine the HR simulation results. The resolved gravity waves and characteristics of TIDs from the HR simulations compare well with available observations in the middle and upper atmosphere. MLT NO, column integrated O/N2 and F-region plasma density show overall improvements. By analyzing the high-resolution simulation results and comparing with control simulations at regular resolution, we elucidate the effects of the resolved gravity waves on the transport from the MLT to the upper thermosphere, by altering both mean circulation and wave mixing.

20th SCOSTEP/PRESTO Online Seminar

Author: Professor Xianglei Huang, University of Michigan, USA
Date and Time: February 13, 2024, 22:00-23:00 UT (17:00-18:00 EST)
Title: "Response of High-latitude Surface Climate to the Variation of Solar Spectral Irradiance: sensitivity studies for a Bottom-up Mechanism"
Link to the video



Abstract: Not only total solar irradiance (TSI) but also spectral solar irradiance (SSI) matter for our climate. On top of spectrally dependent gas absorptions in the atmosphere, different surfaces can have different reflectivity for the visible (VIS) and near-infrared (NIR). The TSI observed by the most recent NASA SSI monitoring mission, TSIS-1, differs from the counterpart used by the CMIP6 climate models by no more than 1 W m?2; however, the SSI difference in a given VIS band (e.g., 0.44?0.63 μm) and NIR band (e.g., 0.78?1.24 μm) can be as large as 4 W m?2 but with opposite signs. We recently showed that such a difference in the spectral partitioning of TSI can cause noticeable differences in the simulated high-latitude surface climate. Using the CESM 2.1.3, we continue this line of research to understand the underlying physical mechanisms for the SSI partitioning to affect the simulated climate. We carried out a series of sensitivity runs by varying the partitioning between the VIS and NIR SSI while keeping the TSI unchanged. Radiative kernels are used to diagnose radiative feedback in response to such configuration (i.e., the different partitioning configurations of the VIS and NIR SSI). Our results show that the surface albedo feedbacks derived from different sensitivity runs are consistent regarding the magnitude and the spatial map. However, the hemispherical averaged broadband albedo changes little throughout all the sensitivity runs. The implications of our findings on future climate-change projection and paleoclimate studies are then discussed.

19th SCOSTEP/PRESTO Online Seminar

Author: Dr. Eugene Rozanov, Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center (PMOD/WRC), Davos, Switzerland
Date and Time: January 23, 2024, 13:00-14:00 UT (14:00-15:00 CET)
Title: "Climate implications of solar irradiance and energetic particles: my way in science"
Link to the video



Abstract: In this talk, I present some observational evidence of the climate response to solar activity variations on different space and time scales. During my scientific career I attempted to explain some of the observed links using numerical models driven by different forcing mechanisms such as UV solar irradiance, precipitating energetic particles, total solar energy influx. The chain which links the forcing and climate response includes a multitude of chemical, physical and dynamical processes and requires application of highly complex numerical models. I will briefly describe the nature of these processes, their climate effects, the level of uncertainty for each mechanism and the most promising directions for future studies of climate response to solar variability.

18th SCOSTEP/PRESTO Online Seminar

Author: Dr. Sergio Dasso, LAMP at Instituto de Astronomía y Física del Espacio, UBA-CONICET, Buenos Aires, Argentina
Date and Time: October 26(Thr), 2023, 12:00-13:00 UT (09:00-10:00 ART, 07:00-08:00 CDT, 21:00-22:00 JST)
Title: "Geo-effectiveness of interplanetary coronal mass ejections: How much can be affected due to their evolution in the heliosphere?"
Link to the video



Abstract: Interplanetary Coronal Mass Ejections (ICMEs) are the solar wind transients producing the major perturbations to the geo-space. Generally larger ICMEs travel faster, has more intense magentic field, and produce stronger perturbations to the geospace and thus, they can produce the most extreme Space Weather events. However, different dynamical processes occurring in the interplanetary medium from their solar launching to their arrival to Earth, can change these properties, and consequently can change their geoeffectiveness. In this seminar I will present the main properties of ICMEs, and those physical processes that produce significant changes on their level of impact. Finally, I will briefly present the effect of ICMEs on ground level flux of galactic cosmic rays, and a new Space Weather laboratory in an Argentine base at the Antarctic peninsula (Marambio), from where the variability of GCRs at ground level can be observed in real time.

17th SCOSTEP/PRESTO Online Seminar

Author: Tomoko Matsuo, University of Colorado at Boulder, USA
Date and Time: Aug 24 (Thr), 2023, 13:00-14:00 UT
Title: "From Earth to the Edge of Space: How Data Assimilation Advances the Science and Engineering of Forecasting Near Earth Space Environments"
Link to the video

Abstract:Prediction serves as the ultimate test of our scientific understanding of geophysical systems. Accurate forecasting of near-Earth space environmental conditions is critical to radio communication, navigation, positioning, and satellite tracking. Effective numerical prediction of the region’s conditions allows us to better protect important space assets and related systems in the event of natural hazards. My research group aims to advance the science and engineering of forecasting, as applied to the Earth’s atmosphere from the ground to near-Earth space environments. Prediction of constantly changing environmental conditions, affected by both space and terrestrial weather, requires a systematic integration of observations with first-principles models using data assimilation. Data assimilation reduces uncertainties in initial conditions and drivers, extending the predictive capability of numerical models of near-Earth space environments. The data assimilation and ensemble-based probabilistic modeling framework being developed can be used for designing of future missions and targeting of observations to maximize scientific returns of observing systems. This seminar will showcase the latest research results and future plans.

16th SCOSTEP/PRESTO Online Seminar

Author: Annilka Seppala, University of Otago, New Zealand
Date and Time: Apr 19 (Wed), 2023, 08:00-09:00 UT
Title: "Solar Influence on climate via energetic particle precipitation: Why is it important and what are the current challenges?"
Link to the video

Abstract: The Sun and our space environment influence the atmosphere though energy inputs from solar radiation and charged particles from the solar wind and Earth’s magnetosphere. Energetic particle precipitation, the rain of electrons and protons of solar and magnetospheric origin, into the Earth’s polar atmosphere was recently included for the first time in the climate simulations informing the Intergovernmental Panel on Climate Change (IPCC). In this seminar, we will go though the ways energetic particle precipitation impacts our atmosphere, and what the currently understood implications on Earth’s climate are. We will also discuss some of the main challenges the scientific community currently faces in pushing towards a realistic representation of the climate effects on global simulations.

15th SCOSTEP/PRESTO Online Seminar

Author: Manolis K. Georgoulis, RCAAM of the Academy of Athens, Greece
Date and Time: Sep 23 (Fri), 2022, 10:00-11:00 UT
Title: "Forecasting the Extreme End of Solar Weather: Flares, Coronal Mass Ejections and SEP Event Complexes"
Link to the video

Abstract: Space Weather, from the near-Sun high corona to the magnetically dominated heliopause, is overwhelmingly due to the solar magnetic activity. This is, to a significant extent, self-similar in nature, featuring lots of small-scale events and few large or extreme events. These originate exclusively from solar active regions and form transients that can incur serious impacts on planetary magnetospheres or reach all the way to the ground via secondary effects or on weakly or non-magnetized solar system bodies. The expansion of the anthroposphere, particularly human space exploration, beyond the low-earth orbit to the cis-lunar environment and presumably further, directly imposes the need for an efficient prediction of the extreme solar weather. I will aim to review the physics and rationale behind these prediction efforts, as well as a brief overview of their current standing and successes. The two main messages I will aim to convey are, first, that inter-connecting between the different domains from the solar photosphere to the heliosphere is arguably the designated way to go, physically, statistically and in terms of a well-founded methodology. There are major challenges in this that I will briefly refer to. Second, the current state-of-the-art on forecasting leaves a lot to be desired. There is heritage on this from interdisciplinary forecasting works, however, that we must exploit, particularly in performance verification and validation, and there are developments in the form of machine learning and artificial intelligence, in general, that can benefit forecasting. Fusing cross-disciplinary and interdisciplinary efforts makes a difference in forecasting solar eruptions, although the overall stochasticity of eruption triggering and practical issues in solar observations remind us that there may be limits on how far we can go.

14th SCOSTEP/PRESTO Online Seminar

Author: Christine Gabrielse, The Aerospace Corporation, USA
Date and Time: Jul 5 (Tue), 2022, 22:00-23:00 UT
Title: "Mesoscales and their Contribution to the Global Response: A Focus on the Magnetotail Transition Region and Magnetosphere-Ionosphere Coupling"
Link to the video

Abstract: How do mesoscale phenomena contribute to the global response of the system? This question has risen to the forefront of the space physics community in recent years, and has been the topic of a Geospace Environment Modeling (GEM) Focus Group since 2017. Specifically, community members have been studying if and how much mesoscale transport in the tail contributes to the more global response at the dipole-stretched transition region with respect to magnetic flux and dipolarization, particle transport and injections, and the substorm current wedge. How this relates to the coupled ionosphere is also an important consideration. This talk will summarize some results that were compiled to answer this question, and poses more questions to the audience to consider with regards to further understanding how mesoscale phenomena contribute to the system global response.

13th SCOSTEP/PRESTO Online Seminar

Author: Theodosios Chatzistergos (SCOSTEP 2022 Distinguished Young Scientist Award Winner), Max Planck Institute for Solar System Research, Germany
Date and Time: Jun 16 (Thu), 2022, 12:00-13:00 UT
Title: "Ca II observations: Exploiting historical treasures for solar activity and variability studies"
Link to the video

Abstract: Most of Earth's external energy originates from the Sun and any change in the amount and distribution of this energy might affect Earth's climate. Therefore, to assess the solar influence on Earth's climate, it is important to have long and reliable records of solar irradiance. But direct measurements only exist since 1978, and models are required to recover the irradiance variability at earlier periods. Irradiance variations on time scales of interest for climate are driven by the evolution of the solar surface magnetic features, such as sunspots and faculae. Thus, to reconstruct past irradiance variability, knowledge of the past changes in sunspot and facular coverage is crucial. Whereas sunspot observations cover a couple of centuries, available facular data are not significantly longer than direct irradiance measurements and thus need to be inferred from other indirect data. This leads to a significant uncertainty in the secular variability of solar irradiance. Full-disc observations of the Sun in Ca II K spectral line have been regularly performed since 1892 at various sites around the world. In fact, beside sunspot records, such data comprise one of the longest sets of solar observations. Ca II K data can provide direct information on facular regions, which is essential for reconstructions of past irradiance variations. Furthermore, due to the connection between Ca II K brightness and solar surface magnetic field strength, such data can also be used to extend available records of unsigned magnetograms back to 1892. Therefore, Ca II K observations have an invaluable potential to enhance our understanding of solar surface magnetism and allow more accurate reconstructions of irradiance variations in the past. Use of Ca II K for such purposes has, however, been rather limited due to numerous, partly severe, problems affecting the images. We have put together a comprehensive collection of 43 Ca II K datasets. We have developed a unique superior method for their consistent processing, removal of artefacts and photometric calibration. The calibrated data have been used to derive the first composite series of plage areas covering the entire 20th century. We have also reassessed the relationship between magnetic field strength and Ca II K brightness, which allows a conversion of the Ca II K observations into maps of unsigned magnetic field. The latter can then been employed to reconstruct the irradiance variations. This opens up the possibility of the reconstruction of the historical irradiance variability from direct independent observations of both sunspots and faculae.

12th SCOSTEP/PRESTO Online Seminar

Author: David J. McComas (SCOSTEP 2022 Distinguished Scientist Award Winner), Princeton University, USA
Date and Time: May 11 (Wed), 2022, 14:00-15:00 UT
Title: "First Solar Cycle of Observations of our Heliosphere’s Interaction with the Very Local Interstellar Medium"
Link to the video

Abstract: Our heliosphere is formed by the supersonic solar wind and entrained interplanetary magnetic field (IMF) flowing outward from the sun and inflating a bubble in the very-local interstellar medium (VLISM). The global interaction of the heliosphere with the VLISM was first observed starting at the end of 2008 by the Interstellar Boundary Explorer (IBEX) mission; IBEX has now observed the 3-dimensional structure of this interaction for over a full solar cycle. IBEX observations include global Energetic Neutral Atoms (ENA) maps of ENAs produced in the heliosheath and VLISM beyond the heliopause. These maps expose a time-variable global heliosphere where solar cycle and even longer temporal variations drive a complex ever-evolving structure that surrounds us and defines our home in the galaxy. This SCOSTEP Distinguished Scientist Award Seminar will describe some of the discoveries and insights about the outer heliosphere and VLISM gleaned from the IBEX mission and link them to the much larger and even more exciting follow-on mission currently under development – the Interstellar Mapping and Acceleration Probe (IMAP).

11th SCOSTEP/PRESTO Online Seminar

Author: Cora Randall, University of Colorado, USA
Date and Time: Feb 10 (Thu), 2022, 14:00-15:00 UT
Title: "Solar-Terrestrial Coupling via Energetic Particle Precipitation"
Link to the video

Abstract: A long-standing goal in the Aeronomy community is to identify and explain the atmospheric processes that indirectly amplify the effects of solar and magnetospheric input. These processes initiate nonlinear feedbacks that couple all regions of the atmosphere, impacting weather and climate throughout. This seminar will focus on how energetic particle precipitation (EPP) influences the middle atmosphere, and how coupling processes amplify these impacts. EPP refers to energetic electrons and protons impinging on the earth’s atmosphere after they have been accelerated by solar and magnetospheric activity. Through complex reaction pathways the precipitating particles produce reactive odd nitrogen (EPP-NO x = N+NO+NO 2 ) and odd hydrogen (EPP-HO x = H+OH+HO 2 ), both of which are important for the catalytic chemistry of ozone. EPP-induced changes in the geographic distribution of ozone, a radiatively important gas, can in theory induce temperature gradients that might impact winds, wave filtering, and the general circulation. This presentation will provide a historical perspective on investigations of EPP impacts on the middle atmosphere, summarize the current understanding, and highlight major areas of uncertainty and needs for the future.

10th SCOSTEP/PRESTO Online Seminar

Author: Tibor Török, Predictive Science Inc., USA
Date and Time: Nov 30 (Tue), 2021, 23:00-24:00 UT
Title: "Understanding and Modeling Solar Eruptions: Where Do We Stand?"
Link to the video

Abstract: Solar eruptions, which are observed as prominence eruptions, flares and coronal mass ejections (CMEs), are the largest energy release processes in the solar system and the main driver of space-weather disturbances at Earth. While over the past decades we have seen tremendous progress in both observations and theory/modeling of solar eruptions, and have learned that these enigmatic phenomena constitute a violent disruption of the coronal magnetic field, there remain a number of unanswered questions, such as of the exact nature of the pre-eruptive magnetic configuration and the physical mechanisms that trigger and drive eruptions. In this seminar talk, I will review our current understanding of these two important aspects. Furthermore, I will discuss recent developments of CME modeling frameworks for community use, and their prospects for serving as physics-based operational space-weather forecast tools in the foreseeable future.

9th SCOSTEP/PRESTO Online Seminar

Author: Richard Eastes, University of Colorado Boulder, USA
Date and Time: Sep 23 (Thu), 2021, 14:00-15:00 UT
Title: "Space Weather in the Thermosphere-Ionosphere System - observations and Insights from the GOLD* Mission (*Global-scale Observations of the Limb and Disk)"
Link to the video

Abstract: The GOLD mission’s spatial-temporal observations of thermospheric composition, density, and temperature, as well as of ionospheric structure and peak density at low-latitudes, provide an unprecedented window into space weather in the Thermosphere-Ionosphere (T-I) system. Imaging the Earth from geostationary orbit at 47.5°W longitude, the GOLD imager provides simultaneous images of thermospheric composition (O/N_2 ) and temperature near 160?km on the dayside every 30 minutes from 06:10 to 23:10 UT (03:00-20:00 local time at the satellite). In addition GOLD images the nighttime equatorial ionization anomaly (EIA) over the Atlantic and South America every evening. Observations of geomagnetic storms, solar eclipses, the nighttime EIA and O_2 density profiles have all provided unanticipated results. Examples include observations of “gravity” waves and global-scale responses to weak geomagnetic activity in the sunlit thermosphere; and in the nighttime EIA, correlations between peak densities and waves in the mesosphere. These observations provide tests of our current understanding of both the T-I system and how it interacts with other regions of the geospace system. The GOLD mission observations and some of the implications for space-weather will be discussed.

8th SCOSTEP/PRESTO Online Seminar

Author: Kristof Petrovay, ELTE Eotvos Lorand University, Hungary
Date and Time: Jun 8 (Tue), 2021, 13:00-14:00 UT
Title: "The Sun making history. The mechanism behind the varying amplitude of the solar cycle"
Link to the video

Abstract: The amplitudes of 11-year solar cycles vary in a wide range, sometimes displaying sudden marked changes from one cycle to the next. The decadal time scales involved are comparable to the life cycle of space missions -and of human beings. The impact of solar activity on space climate and terrestrial climate calls for a prediciton capability, a precondition for which is a good understanding of the mechanism driving intercycle variations in the solar dynamo. The past decade has seen significant advance in this direction. A promising scenario has emerged in which intercycle variations are driven by the vagaries of magnetic flux emergence from the solar interior into the atmosphere in the form of active regions (ARs). A variety of nonaxisymmetric dynamo models incorporating individual Ars have been developed, along with surface flux transport models used for prediction relying on the polar magnetic field as a proxy for the next cycle amplitude. The results indicate that a combination of nonlinear feedback effects and stochastic noise may govern the run-of-the-mill intercycle variations, while a low number of large "rogue" ARs with unusual properties bear the brunt of the responsibility for large, unexpected intercycle changes. The talk will review these developments, focusing on the issue of how the properties of individual ARs determine their "dynamo effectivity", i.e. how they will impact on the polar magnetic field built up during a cycle that will serve as the seed for the next solar cycle. The importance of maintaining and, where possible, reconstructing long term data sets on solar activity will be stressed and some aspects of the Sun's unexpected historical changes will be discussed.

7th SCOSTEP/PRESTO Online Seminar

Author: Franz-Josef Lübken (SCOSTEP 2021 Distinguished Service Award Winner), Leibniz-Institute of Atmospheric Physics, Germany
Date and Time: May 21 (Fri), 2021, 12:00-13:00 UT
Title: "Physics at the edge between Earth's atmosphere and space"
Link to the video

Abstract: The importance of basic physical processes in the atmosphere changes fundamentally in the upper mesosphere/lower thermosphere (UMLT, appr. 80 to 130 km) primarily due to the reduction of gas density being orders of magnitude smaller compared to the troposphere. For example, molecules are no longer in thermodynamic equilibrium with radiation, and mixing ratios of inert species change with height. Furthermore, gravity waves being generated in the troposphere achieve large amplitudes in the UMLT, get instable and produce turbulence. This in turn causes a modification of the general circulation which leads to a substantial cooling (heating) in the summer (winter) mesosphere. The summer mesopause (appr. 90 km) at polar latitudes is special in many ways. It is the coldest place in the Earth's atmosphere (appr. 130 K), nearly 100 K colder compared to the radiatively controlled state (despite permanent sunshine) which is a consequence of the `residual circulation' introduced above. This region is very sensitive to dynamical forcing, in particular due to gravity waves and tides, and can therefore be used to test physical descriptions. The extremely low temperatures at the summer mesopause lead to ice particles known as noctilucent clouds (NLC) or polar mesosphere clouds (PMC). The same ice particles produce very strong radar echoes (PMSE, polar mesosphere summer echoes). NLC, PMSE, and PMC are studied in detail by lidars, radars, and satellites, respectively, which has clarified some important physical processes involved. Since ice particles are very sensitive to atmospheric temperatures and water vapor, they are proposed to be sensitive indicators for climate change effects in the middle atmosphere (MA). Indeed, large temperature trends (cooling) are observed in the middle atmosphere at mid latitudes, much larger (in sign) compared to the warming in the troposphere. However, models suggest that the summer mesopause is the only region in the entire Earth's MA where warming (instead of cooling) should prevail. In the presentation, some basic physical processes leading to the thermal structure of the upper atmosphere and to ice particles are explained including the role of dynamical forcing, solar cycle effects, and trends due to climate change.

6th SCOSTEP/PRESTO Online Seminar

Author: Mateja Dumbović (SCOSTEP 2020 Distinguished Young Scientist Award Winner), University of Zagreb, Croatia
Date and Time: Jan 19 (Tue), 2021, 12:00-13:00 UT
Title: "Utilizing galactic cosmic rays as signatures of interplanetary transients"
Link to the video

Abstract: Coronal mass ejections (CMEs), interplanetary shocks and corotating interaction regions are drivers of heliospheric variability and cause various interplanetary as well as planetary disturbances. One of their very common in-situ signatures are short-term reductions in the galactic cosmic ray (GCR) flux (i.e. Forbush decreases). These phenomena are caused by the interaction of GCRs with a magnetic structure, therefore it is expected that different types of interplanetary substructures cause different types of GCR depressions, allowing us to distinguish between shock/sheath, flux rope and SIR-type of FDs. Moreover, since the interaction of GCRs and CME magnetic structure (presumably flux rope) occurs all the way from Sun to Earth, FDs should also reflect the evolutionary properties of CMEs, which is supported by the results from our recent modeling efforts. In the light of these recent studies, we will discuss if and how GCR depressions can be used more efficiently as signatures of interplanetary transients.

5th SCOSTEP/PRESTO Online Seminar

Author: Q.-G. Zong (SCOSTEP 2020 Distinguished Scientist Award Winner), Peking University, China
Date and Time: Jan 14 (Thu), 2021, 00:00-01:00 UT
Title: "Magnetospheric Response to Interplanetary Shocks: ULF Wave-Particle Interaction Perspective"
Link to the video

Abstract: Impact of interplanetary shocks on the Earth’s magnetosphere manifests many fundamental processes in space physics including generation of electromagnetic waves, plasma heating, and energetic particle acceleration. This lecture summarizes our present understanding of the magnetospheric response to interplanetary shocks in the aspects of interaction of shock generated ULF waves with radiation belt electrons, ring current ions, and plasmaspheric plasma based on in-situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations. Magnetospheric response to interplanetary shocks is not a “one-kick” scenario. Interplanetary shocks compress the magnetosphere and generate different types of waves including poloidal mode ultra-low frequency (ULF) waves in the magnetosphere. Plasma heating and energetic particle acceleration start nearly immediately after the impact of interplanetary shocks and can last several hours. The fast acceleration of radiation belt electrons and ring current ions usually contain two contributing steps: (1) the initial adiabatic acceleration due to the magnetospheric compression; (2) followed by resonant acceleration by global or localized poloidal ULF waves. A general theory of drift and drift-bounce resonance between charged particles and growing or decaying localized ULF waves has been developed to interpret in-situ spacecraft observations. The observed features associated with waves, such as the energy dispersion as well as boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma, can be explained in the framework of this general theory. It is worth noting that poloidal ULF waves are much more efficient than toroidal ULF waves in accelerating and modulating radiation belt electrons (fundamental mode) and ring current ions (second harmonic). The results presented in this lecture can be applied to the solar wind interaction with other planets such as Mercury, Jupiter, Saturn, Uranus, and Neptune, as well as other magnetized astrophysical objects.

4th SCOSTEP/PRESTO Online Seminar

Author: Thomas Immel, University of California, Berkeley, USA
Date and Time: Nov 17 (Tue), 2020, 23:00-24:00 UT
Title: "The Ionospheric Connection Explorer - Results from the first year on orbit"
Link to the video

Abstract: The NASA Ionospheric Connection Explorer has provided a full year of coordinated measurements of the ionosphere and thermosphere, with excellent performance of its instruments and the observing platform. Its measurements support ICON’s specific mission objectives to 1) determine the source of strong day-to-day variability in ionospheric densities, 2) determine how large-scale atmospheric waves propagate upward and interact with the ionosphere, and 3) understand how these effects interact with and modify geomagnetic storm phenomena. We will discuss some of the more remarkable effects observed by ICON, and how the analysis of these data is leading to new understanding of the behavior of the ITM system. This will include a brief review of comparisons to other measurements and a summary of validation efforts for improved data products.

3rd SCOSTEP/PRESTO Online Seminar

Author: Joe Borovsky, Space Science Institute, USA
Date and Time: Sep 10 (Thu), 2020, 22:00-23:00 UT
Title: "Developing a Highliy Predictable Geomagnetic Index to Gauge Magnetospheric Activity and Space Weather"
Link to the video

Abstract: A composite geomagnetic index that is highly predictable from a knowledge of the upstream solar wind is being developed using the mathematical technique “canonical correlation analysis”. This “canonical” geomagnetic index will be constructed from multiple existing geomagnetic indices measuring different current systems and activity types in the magnetosphere-ionosphere system. The canonical index will describe global activity in the magnetosphere-ionosphere system. Of the many possibilities, the one “canonical” index will be selected based on high predictability and on availability of the geomagnetic indices used. This canonical index will be robust, in that it is as well predicted for high activity levels as it is for low activity, and is expected to be well predicted for as-yet-unseen extreme solar-wind conditions. Once the canonical index is derived, along with its canonical solar-wind driver function), superposed-epoch analysis and other statistical techniques will be used to familiarize the index by gauging CME-driven storms, high-speed-stream-driven storms, substorms, steady magnetospheric convection intervals, etc.

2nd SCOSTEP/PRESTO Online Seminar

Author: Ilya Usoskin, University of Oulu, Finland
Date and Time: Jul 20 (Mon), 2020, 12:00-13:00 UT
Title: "Extreme solar events: A new paradigm"
Link to the video

Abstract: The Sun provides the energy for life on Earth and always shine in seemingly the same way, as was believed until recently. But we also know that it can produce sporadic eruptive events, such as solar bright flares and huge coronal mass ejections. Such events are often accompanied by the so-called solar particle storms, which are short-term events with very intense fluxes of solar energetic particles (SEPs) observed in space near Earth. These events remained beyond our detection abilities even several decades ago, but now we know that they may pose a serious threat to our modern technological society and even human lives outside the protective Earth's atmosphere and magnetosphere. Our knowledge of such events was limited to nearly 70 years, with the strongest directly observed solar particle storm occurred on 23-Feb-1956 with a ~5000 % enhancement over the galactic cosmic-ray background. The following questions may arise: Can even stronger storms appear? How much stronger and how often? What could be the "worst-case scenario''? What consequences of such events would be for modern society? The era of direct measurements is too short to answer these questions, but nature gives us a unique chance to get answers. Thanks to the recent discoveries, we know that there are extreme events on the Sun on the large-time scale and on distant sun-like stars. Here we present an overview of the current state of the art in the study of extreme SEP events based on different indirect methods, including cosmogenic isotope (14C, 10Be, 36Cl) in terrestrial archives and lunar rocks, as well as an extensive statistic of the superflares on sun-like stars.

1st SCOSTEP/PRESTO Online Seminar

Author: Kanya Kusano, Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Japan
Date and Time: May 26 (Tue), 2020, 12:00-13:00 UT
Title: "A challenge to Physics-based Prediction of Giant Solar Flares"
Link to the video

Abstract: Solar flares are catastrophic explosions in the solar corona and may potentially cause a severe space weather disaster. However, because the onset mechanism of solar flares is not yet well elucidated, most of the flare forecasts in operation rely on empirical methods. We recently developed a new physics-based model, called the κ-scheme, for predicting giant solar flares as one of the major outcomes of the Project for Solar-Terrestrial Environment Prediction (PSTEP), which is the Japanese nation-wide project for space weather and space climate study. Theκ-scheme is able to predict imminent giant solar flares through the critical condition of magnetohydrodynamic (MHD) instability triggered by magnetic reconnection. An analysis of the largest solar flares in solar cycle 24 indicates that the κ-scheme can provide precise information, including location and size, of possible giant solar flares with a small exception. Through this study, we also discovered that the magnetic twist flux density in the vicinity of the magnetic polarity inversion line (PIL) on the solar surface plays a crucial role in determining when, where, and how large solar flares may occur. Finally, we will discuss how important is the development of physics-based prediction to improve our predictive capability and the scientific understanding of solar-terrestrial system dynamics.