Space Physics Seminar

semester, 2017

Tuesday, January 17th 2017
09:30 am:
Organizational Meeting

Tuesday, January 24th 2017
12:20 pm:
Speaker: James Mason, University of Colorado
Subject: The Success and the Science of the Student-Built MinXSS Solar CubeSat

CU Boulder and LASP have a long history of involving students in every aspect of science spacecraft production. The most recent incarnation is the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat, which was sent to the International Space Station with resupply cargo and then deployed from the airlock on 2016 May 16. Students were heavily involved in the design, manufacturing, assembly, extensive testing, delivery to Houston; and continue to be involved in the mission operations, data pipeline production, and science analysis. CubeSats are comparatively low cost for spacecraft and as such the programs tend to accept more risk, the result of which is a higher rate of failure. The ongoing MinXSS-1 mission has exceeded comprehensive success criteria, has been featured by NASA, won the 2016 AIAA SmallSat mission of the year award, and is the first science CubeSat funded by NASA to be launched. I’ll touch on how we made sure MinXSS would be a success. I’ll also describe some of the early science results from the MinXSS-1 mission, which focus on the energetic processes that occur in the solar corona. Finally, I’ll discuss what we wish we would have done on MinXSS-1; fortunately, we built two satellites so we can make those wishes a reality on MinXSS-2, scheduled to launch in the first half of 2017.

Tuesday, January 31st 2017
12:20 pm:
Speaker: Sophie Musset, University of Minnesota
Subject: Energetic electrons acceleration and transport in the corona (via X-ray diagnostics): from RHESSI data analysis to the preparation of the STIX experiment on Solar Orbiter.

An important fraction of the magnetic energy released during solar flares is transmitted to ambient particles which can be accelerated to energies of several hundreds of keV to a few keV for electrons, and several tens to a few hundreds of MeV for ions. Yet, we only poorly know the details of the physical mechanisms responsible for fast and efficient particle acceleration, and for the transport of energetic particle between acceleration sites and interaction sites where they emit electromagnetic radiation. I will present the work conducted during my PhD preparation at the Observatoire de Paris, in the context of the study of solar energetic electron acceleration and transport in the solar corona through X-ray diagnostics.

In the first part of the seminar, I will present how I investigated the link between energetic electron X-ray emissions and electric current densities measured at the photospheric level during X-class solar flares. This work shows that energetic electron acceleration sites are located above the highest current densities for several X-class flares. A common evolution of X-ray emission and photospheric electric currents has also been shown during a flare (Musset et al 2015). In a second study, I examined the effect of transport in the corona on the energetic electron distribution during a flare. A fraction of energetic electrons are trapped in the coronal part of the flare loop, and it can be explained with a diffusive transport model. Combining X-ray and radio observations, the scattering mean free path was estimated at different electrons energies for the first time in the solar corona, and shown to be decreasing with increasing energy.

In the second part of the seminar, I will present the STIX instrument onboard Solar Orbiter, which will provide X-ray diagnostics of the sources of energetic electrons in the solar corona. I will briefly present the challenges and some of the advances made in term of onboard and analysis software for this experiment.

Tuesday, February 7th 2017
12:20 pm:
Speaker: Colin Waters, University of Newcastle
Subject: Spatial and temporal development of geomagnetic induced currents (GICs) during the 2015 St Patrick's Day storm

Geomagnetic storms are often associated with elevated solar activity such as coronal mass ejections (CMEs) and sudden impulses (SI). The 17 March, 2015 storm was a G4 level (severe) event with duration of ~18 hours, commencing 14 UT as a result of a CME that occurred on the Sun around 02 UT, 15 March.
The availability of experimental data for monitoring geomagnetic storm events is limited by both instrument response and location. The limitations of comprehensive spatial coverage is a common difficulty. This is particularly acute when attempting to predict storm effects on GIC sensitive infrastructure such as electricity supply grids. Global data collection at low Earth orbit (LEO) can be achieved using engineering magnetometer data obtained from the Iridium satellite constellation which for the first time, are combined with global ground based magnetic field data. These data sets are discussed in the context of the spatial/temporal problem in GIC research and the efforts to predict GIC impacts on electricity supply infrastructure.

Tuesday, February 14th 2017
12:20 pm:
There will be no seminar this week.

Friday, February 24th 2017
11:00 am:
Speaker: Daniel Baker
The seminar will be held on Friday, this week only.
11:15 am:
Speaker: Daniel Baker, University of Colorado
Subject: Studying Relativistic Particle Acceleration and Loss in Our Cosmic Backyard: Van Allen Probes Radiation Belt Exploration
Please note change of time, room and day for the seminar, this week only.

Early observations of the Earth’s radiation environment suggested that the Van Allen belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies showed that electrons in the energy range 100 keV < E< 1 MeV often populated both the inner and outer zones with a pronounced “slot” region relatively devoid of energetic electrons existing between them. The energy distribution, spatial extent and particle species makeup of the Van Allen belts has been subsequently explored by several space missions. However, recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed wholly unexpected properties of the radiation belts, especially at highly relativistic (E > 2 MeV) and ultra-relativistic (E > 5 MeV) kinetic energies. In this talk we show using high spatial and temporal resolution data from the Relativistic Electron-Proton Telescope (REPT) experiment on board the Van Allen Probes that multiple belts can exist concurrently and that an exceedingly sharp inner boundary exists for ultra-relativistic electrons. Using additionally available Van Allen Probes data, we demonstrate that these remarkable features of energetic electrons are not due to a physical boundary within Earth’s intrinsic magnetic field. Rather it likely that human-generated electromagnetic transmitter wave fields produce such effects suggesting that human-made wave-particle scattering effects deep inside the Earth’s magnetosphere can contribute to an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate

Tuesday, February 28th 2017
12:20 pm:
Speaker: John Dombeck, Physics, U Minnesota
Subject: Field-Aligned Currents and Auroral Precipitation Mechanisms in the Earth's Magnetosphere

Field-aligned currents (FACs) provide a fundamental driver and means of Magnetosphere-Ionosphere (M-I) coupling. These currents need to be supported by local physics along the entire field line generally with quasi-static potential structures, but also to support the time-evolution of these structures and currents Alfvén waves are required which can produce Alfvénic electron acceleration. In regions of upward current, precipitating auroral electrons are accelerated earthward. These processes can result in ion outflow, changes
in ionospheric conductivity, and affect the particle distributions on the field line, affecting the M-I coupling processes supporting the individual FACs and potentially the entire FAC system. The FAST mission was well suited to study both the FACs and the electron auroral acceleration processes. We present the results of the comparisons between meso- and small-scale FACs determined from FAST using the method of Peria, et al., 2000, and our FAST auroral acceleration mechanism study when such identification is possible for the entire ~13 year FAST mission.

Tuesday, March 7th 2017
12:20 pm:
Speaker: Terry J. Jones, U Minnesota, MN Institute for Astrophysics
Subject: Magnetic Fields, Grain Alignment, and You

Observations of polarization caused by dust grains aligned with the
magnetic field is a major tool for studying the magnetic field geometry
in regions ranging in size from entire galaxies, down to planetary
systems and stellar winds. The alignment mechanism, however, has eluded
astronomers for over 50 years. After these years of frustration, we now
seem to be closing in on an understanding of the alignment mechanism,
which I will discuss.

Tuesday, March 21st 2017
12:20 pm:
Speaker: Scott Thaller
Subject: Evidence for modulations of the cold plasma density and convection in the inner magnetosphere being driven at the solar rotation period

"In this talk I will present work we have done with Van Allen Probes data which provides strong evidence for solar rotation modulation of the plasmapause location, dawn-dusk electric field, and cold plasma density from 2.5 < L < 5. In this research we show that the solar rotation modulation of the inner magnetosphere is prominent during the declining phase of the solar cycle when there is a heightened occurrence of fast solar wind streams routinely passing over the earth at the solar rotation period, called Co-rotating Interaction Regions (CIRs). The occurrence of enhanced periods of geomagnetic activity being driven by the CIRs every ~27 days leads to modulation of the plasmasphere on that timescale. In contrast, during solar maximum when the geomagnetic activity in the magnetosphere is more likely to be driven by CMEs, the solar rotation modulation is less prominent, if at all present. I will also present research we have conducted on the cold plasma outflows that occur during geomagnetic activity, including outflows driven at the solar rotation period.

Tuesday, March 28th 2017
12:20 pm:
There will be no seminar this week.

Tuesday, April 4th 2017
12:20 pm:
There will be no seminar this week; group should attend Adam Kowalski's MIfA colloquium on Friday

Tuesday, April 11th 2017
12:20 pm:
Speaker: Dr. Andreas Keiling, Space Science Lab, UCB
Subject: Substorms in the Solar System and their Periodicity

Spacecraft observations have established that all magnetized planets in our solar system (Mercury, Earth, Jupiter, Saturn, Uranus, and Neptune) interact strongly with the solar wind and possess well-developed magnetotails. Magnetotails are the site of many dynamic processes critical to the transport of mass, momentum, energy, and magnetic flux. The great differences in solar wind conditions, planetary rotation rates, ionospheric conductivity, and physical dimensions from Mercury’s small magnetosphere to the giant magnetospheres of Jupiter and Saturn provide an outstanding opportunity to extend our understanding of the influence of these factors on magnetotail processes and structure. Among the many differences and similarities, in this presentation I will provide an (sketchy) overview of magnetospheric substorms, together with new results on substorm periodicity.

Tuesday, April 18th 2017
12:20 pm:
There will be no seminar this week.

Friday, April 21st 2017
11:15 am:
Speaker: Dr. Brian J. Anderson, Johns Hopkins University Applied Physics Lab
Subject: Field-aligned auroral current systems at Earth and Mercury: Implications for magnetic convection at Mercury

Birkeland currents are present at both Earth and Mercury and the differences in currents reflect fundamental differences in the convection dynamics of these systems. At Earth, the conductive ionosphere and the high altitude magnetosphere are linked with these currents through the Pedersen conductance which closes the currents in the ionosphere and through magnetospheric plasma that carries the Region 2 currents between the evening and morning sectors, shielding the inner magnetosphere from the convection potential. The currents reflect the convection of magnetic flux from the dayside, over the polar caps into the magnetotail, and subsequently sunward in the tail to the dayside. At Mercury, Birkeland currents close through the planet itself with at least half of the current reaching the core to close laterally at polar latitudes. There is no evidence of Region 2 currents at Mercury implying that the magnetosphere and planet itself are not shielded from the convection cycle and suggesting that the planet also participates in the return convection although how this is actually accomplished is not known.

Tuesday, April 25th 2017
12:20 pm:
There will be no seminar this week.

Tuesday, May 2nd 2017
12:20 pm:
Speaker: Cindy Cattell, University of Minnesota
Subject: What new information can high frequency waves tell us about the July 2012 'Carrington' event? Preliminary results from STEREO

Friday, May 19th 2017
1:00 pm:
Speaker: Tadayuki Takahashi, JAX/ISAS and the University of Tokyo
Subject: New hard X-ray and gamma-ray detectors for future high energy astronomy missions

This seminar will be of interest to anyone interested in semiconductor detectors, high-energy astronomy, space physics, and other X-ray measurements.

Tuesday, September 5th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Nicole Vilmer, LESIA, Paris Observatory
Subject: Radio Diagnostics of Energetic Electron Beams and of Magnetic Fields in the Corona


Faculty Host: Lindsay Glesener

Tuesday, September 12th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Andrew Inglis, NASA/Goddard
Subject: Characterizing discrete power in solar flares and the magnetosphere using the AFINO algorithm.

The search for discrete power in timeseries is an important goal throughout many areas of Heliophysics, from the physics of solar flares to understanding waves in the Earth's magnetosphere. The AFINO (Automated Flare Inference of Oscillations) code is a novel algorithm which was originally developed to search for periodic signatures in solar flares using a model comparison technique. We present the original results of AFINO, which was used to carry out a large-scale search for quasi-periodic pulsations in 675 M- and X-class flares observed by GOES in 1-8 Å soft X-rays between 2011 February 1 and 2015 December 31. For the first time, we are able to estimate the occurrence rate of periodic signatures in flares, their characteristic periods, and their dependence on other flare parameters.

Since then, we have adapted AFINO in order to search for regions of discrete and broadband wave power in the Earth's magnetosphere, in particular to search for ULF waves. ULF waves play a fundamental role in the dynamics of the inner-magnetosphere during geomagnetic storms and in particular the dynamics of energetic electron in the outer radiation belt. Here, we show the results of AFINO applied to GOES magnetometer data, and also to a moderate geomagnetic storm observed by MMS. By analyzing multiple magnetic field components simultaneously we can determine which types of ULF wave modes dominate at different L-shells, and their typical properties. These results can be combined with a novel method utilizing the close separation of the MMS spacecraft and cross-phase between wave signals to estimate the ULF wave azimuthal wave number m.

Faculty Host: Lindsay Glesener

Tuesday, September 19th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Tuesday, September 26th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
There will be no seminar this week.

Tuesday, October 3rd 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Mark Engebretson, Augsburg College
Subject: Recent observational studies of EMIC waves

Tuesday, October 10th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
Speaker: Bob Lysak and Yan Song, University of Minnesota
Subject: Report on the 13th International Conference on Substorms

Tuesday, October 17th 2017
12:20 pm:
Space Physics Seminar in Tate 301-20
To be announced.

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