Calendar

Oct
16
Fri
Colloquium: Doug Biesecker
Oct 16 @ 3:15 pm – 4:15 pm
Colloquium: Doug Biesecker @ BX102

Why Space Weather Matters and How Forecasting Will Improve in the DSCOVR Era

Doug Biesecker, NOAA/NWS/Space Weather Prediction Center

Space Weather is a growing enterprise, with growing recognition of its importance inside and outside government.  The largest concern is with the electric power grid, but impacts to Global Positioning Systems (GPS) are also significant.  Other areas of impact include satellites and human space flight, and high frequency communication for aviation, mariners, and emergency responders, among many.  The NOAA National Weather Service’s Space Weather Prediction Center (SWPC) is the nation’s official source of space weather watches, warnings and alerts.  SWPC does this with a 24×7 staffed operation that monitors the Sun, solar wind, and geospace environment taking advantage of a broad suite of observations and models to provide the best forecasts possible.  In conjunction with the growing recognition of space weather, NOAA launched its first mission, the Deep Space Climate Observatory (DSCOVR), out of the Earth’s orbit to an orbit about the L1 Lagrange point.  This is also NOAA’s first satellite mission where space weather is the primary mission and DSCOVR marks the first of what is expected to be a long series of space weather monitoring satellites.  NOAA is also bringing numerical space weather models into the mix of models running on the nation’s supercomputers.  Numerical space weather models have demonstrated the ability to improve the onset time of space weather storms and will, for the first time, allow regional geomagnetic forecasting.  Instead of describing conditions on Earth with a single number, customers will have forecasts tailored to their location.

 

Feb
12
Fri
Colloquium: Lauren Woolsey
Feb 12 @ 3:15 pm – 4:15 pm
Colloquium:  Lauren Woolsey @ BX102

Magnetic Influences on Coronal Heating and the Solar Wind

Lauren Woolsey, Harvard University

 

Abstract

The physical mechanism(s) that generate and accelerate the solar wind have not been conclusively determined after decades of study, though not for lack of possibilities. The long list of proposed processes can be grouped into two main paradigms: 1) models that require the rearranging of magnetic topology through magnetic reconnection in order to release energy and accelerate the wind and 2) models that require the launching of magnetoacoustic and Alfvén waves to propagate along the magnetic field and generate turbulence to heat the corona and accelerate the emanating wind. After a short overview of these paradigms, I will present my ongoing dissertation work that seeks to investigate the latter category of theoretical models and the role that different magnetic field profiles play in the resulting solar wind properties with Alfvén-wave-driven turbulent heating. I will describe the computer modeling in 1D and 3D that I have done of bundles of magnetic field (flux tubes) that are open to the heliosphere, and what our results can tell us about the influences of magnetic field on the solar wind in these flux tubes, including the latest time-dependent modeling that produces bursty, nanoflare-like heating. Additionally, I will present the latest results of our study of chromospheric network jets and the magnetic thresholds we are finding in magnetogram data.

Mar
3
Fri
Colloquium: Bart De Pontieu
Mar 3 @ 3:15 pm – 4:15 pm
Colloquium: Bart De Pontieu @ BX 102

Interface Region Imaging Spectrograph Views of How the Solar Atmosphere is Energized

Dr. Bart De Pontieu, Lockheed Martin

At the interface between the Sun’s surface and million-degree outer atmosphere or corona lies the chromosphere. At 10,000K it is much cooler than the corona, but also many orders of magnitude denser. The chromosphere processes all magneto-convective energy that drives the heating of the million-degree outer atmosphere or corona, and requires a heating rate that is at least as large as that required for the corona. Yet many questions remain about what drives the chromospheric dynamics and energetics and how these are connected to the transition region and corona.

The Interface Region Imaging Spectrograph (IRIS) is a NASA small explorer satellite that was launched in 2013 to study these questions. I will review recent results from IRIS in which observations and models are compared to study the onset of fast magnetic reconnection in the solar atmosphere, the generation of violent jets and how they feed plasma into the hot corona, and the role of nanoflares in heating the corona.

Mar
10
Fri
Colloquium: Hazel Bain
Mar 10 @ 3:15 pm – 4:15 pm
Colloquium: Hazel Bain @ BX 102

Antarctic high altitude balloon observations of solar flares: Life and work on the ice

Dr. Hazel Bain, University of California, Berkeley

 

The Gamma-Ray Imager/Polarimeter for solar flares (GRIPS) instrument is a balloon-borne telescope designed to study particle acceleration in solar flares. The process through which stored magnetic energy is released and particles are accelerated to high energies in solar flares is not well understood. Hard x-rays and gamma-rays are direct signatures of these accelerated particles and can be used as a proxy to investigate particle acceleration mechanisms in these explosive events.

In the austral summer of 2016, GRIPS began its inaugural flight from NASA’s Long Duration Balloon (LDB) facility just outside McMurdo, Antarctica. During the 12 day flight, the balloon was carried around the Antarctic continent by the seasonal stratospheric polar vortex. At the end of the 2016 season, the data vaults were recovered however due to the lateness of the season a full recovery was scheduled for the following year.

In this talk I will discuss the GRIPS instrument design and science goals, the process of testing and integration leading up to a balloon launch, the inaugural flight and subsequent instrument recovery this year from the GRIPS landing site out in Antarctica’s “flat white”. I’ll also talk a little bit about life and work on the ice.

Apr
24
Mon
Pizza Lunch: Laurel Farris
Apr 24 @ 12:30 pm – 1:30 pm
Pizza Lunch: Laurel Farris @ AY 119

Determining the size of coronal bright points using cross-correlation methods

Laurel Farris

 

Sep
21
Fri
Colloquium: Dave Thilker (Host: Rene Walterbos)
Sep 21 @ 3:15 pm – 4:15 pm
Colloquium: Dave Thilker (Host: Rene Walterbos) @ BX102

Fresh Perspectives on Star Formation from LEGUS, the Legacy ExtraGalactic Ultraviolet Survey

David Thilker, Johns Hopkins University

The Legacy ExtraGalactic Ultraviolet Survey (LEGUS) was a Cycle 21 Large Treasury HST program which obtained ~parsec resolution NUV- to I-band WFC3 imaging for 50 nearby, representative star-forming Local Volume galaxies, with a primary goal of linking the scales of star formation from the limit of individual stars, to clusters and associations, eventually up through the hierarchy to giant star forming complexes and galaxy-scale morphological features.

I will review the basics of the survey, public data products and science team results pertaining to clusters and the field star hierarchy.  I will then describe work to optimize photometric selection methods for massive main sequence O star candidates and LBV candidates, in the former case establishing a means to statistically constrain the fraction of O stars in very isolated locales.  I will introduce new ideas on how to quantify the complex spatio-temporal nature of hierarchical star formation using multi-scale clustering methods. The first steps of this work have yielded a landmark OB association database for 36 LEGUS target fields (in 28 of the nearest available galaxies), with tracer stellar populations selected and interpreted uniformly.  I will finish with discussion of a pilot HST program to demonstrate remarkably increased survey efficiency of WFC3 UV imaging enabled by use of extra-wide (X) filter bandpasses.  Such efficiency is required as we move beyond LEGUS and begin to rigorously explore low surface brightness star-forming environments where canonical results for the IMF and cluster formation efficiency are increasingly called into question.