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.

Sep
20
Tue
Colloquium Thesis Proposal: Ethan Dederick
Sep 20 @ 3:00 pm – 4:00 pm
Colloquium Thesis Proposal: Ethan Dederick @ Science Hall 310

Utilizing Planetary Oscillations to Constrain the Interior Structure of the Jovian Planets

Ethan Dederick

Seismology has been the premier tool of study for understanding the
interior structure of the Earth, the Sun, and even other stars. Yet in this
thesis proposal, we wish to utilize these tools to understand the interior
structure of the Jovian planets, Saturn in particular. Recent observations
of spiral density structures in Saturn’s rings caused by its oscillations
have provided insight into which modes exist within Saturn and at what
frequencies. Utilizing these frequencies to compare to probable mode can-
didates calculated from Saturn models will also us to ascertain the interior
profiles of state variables such as density, sound speed, rotation, etc. Using
these profiles in a Saturn model, coupled with tweaking the interior struc-
ture of the model, i.e. the inclusion of stably stratified regions, should
allow us to explain which modes are responsible for the density structures
in the rings, as well as predict where to look to find more such structures.
In doing so, we will not only have a much greater understanding of Sat-
urn’s interior structure, but will have constructed a method that can also
be applied to Jupiter once observations of its mode frequencies become
available. In addition, we seek to explain if moist convection on Jupiter is
responsible for exciting its modes. We aim to do this by modeling Jupiter
as a 2D harmonic oscillator. By creating a resonance between moist con-
vective storms and Jovian modes, we hope to match the expected mode
energies and surface displacements of Jupiter’s oscillations.

Mar
2
Thu
Colloquium: Jack Burns (Host: Nancy Chanover)
Mar 2 @ 3:15 pm – 4:15 pm
Colloquium: Jack Burns (Host: Nancy Chanover) @ Domenici Hall Room 106

Cosmology from the Moon: The Dark Ages Radio Explorer (DARE)

Dr. Jack Burns, University of Colorado Boulder

In the New Worlds, New Horizons in Astronomy & Astrophysics Decadal Survey, Cosmic Dawn was singled out as one of the top astrophysics priorities for this decade. Specifically, the Decadal report asked “when and how did the first galaxies form out of cold clumps of hydrogen gas and start to shine—when was our cosmic dawn?” It proposed “astronomers must now search the sky for these infant galaxies and find out how they behaved and interacted with their surroundings.” This is the science objective of DARE – to search for the first stars, galaxies, and black holes via their impact on the intergalactic medium (IGM) as measured by the highly redshifted 21-cm hyperfine transition of neutral hydrogen (HI). DARE will probe redshifts of 11-35 (Dark Ages to Cosmic Dawn) with observed HI frequencies of 40-120 MHz. DARE will observe expected spectral features in the global signal of HI that correspond to stellar ignition (Lyman-α from the first stars coupling with the HI hyperfine transition), X-ray heating/ionization of the IGM from the first accreting black holes, and the beginning of reionization (signal dominated by IGM ionization fraction). These observations will complement those expected from JWST, ALMA, and HERA. We propose to observe these spectral features with a broad-beam dipole antenna along with a wide-band receiver and digital spectrometer. We will place DARE in lunar orbit and take data only above the farside, a location known to be free of human-generated RFI and with a negligible ionosphere. In this talk, I will present the mission concept including initial results from an engineering prototypes which are designed to perform end-to-end validation of the instrument and our calibration techniques. I will also describe our signal extraction tool, using a Markov Chain Monte Carlo technique, which measures the parameterized spectral features in the presence of substantial Galactic and solar system foregrounds.

 

Oct
25
Fri
Colloquium: Shun Karato (Host: Jason Jackiewicz)
Oct 25 @ 3:15 pm – 4:15 pm
Colloquium: Shun Karato (Host: Jason Jackiewicz) @ BX102

Solving the Puzzles of the Moon

Shun Karato, Yale University

After 50 years from the first landing of men on the Moon, about 380 kg of samples were collected by the Apollo mission. Chemical analyses of these samples together with a theory of planetary formation led to a “giant impact” paradigm (in mid 1970s). In this paradigm, the Moon was formed in the later stage of Earth formation (not the very late stage, though), when the proto-Earth was hit by an impactor with a modest size (~ Mars size) at an oblique angle. Such an impact is a natural consequence of planetary formation from a proto-planetary nebula. This collision may have kicked out mantle materials from the proto-Earth to form the Moon. This model explains mostly rocky composition of the Moon and the large angular momentum of the Earth-Moon system. High temperatures caused by an impact likely removed much of the volatile components such as water.

However, two recent geochemical observations cast doubt about the validity of such a paradigm. They include (i) not-so-dry Moon suggested from the analysis of basaltic inclusions in olivine, and (ii) the high degree of similarities in many isotopes. The first observation is obviously counter-intuitive, but the second one is also hard to reconcile with the standard model of a giant impact, because many models show that a giant impact produces the Moon mostly from the impactor. In this presentation, I will show how one can solve these puzzles by a combination of physics/chemistry of materials with some basic physics of a giant impact.