Tagged: Center for Space Physics

CSP Seminar Speaker: James Clemmons (The Aerospace Corporation)

April 25th, 2011 in In the News

Speaker: James Clemmons
Affiliation: The Aerospace Corporation

Title: Recent Analyses of In-Situ Thermospheric Measurements

Date: Thursday, April 28, 2011
Time: 3:30 PM Refreshments in CAS 500, 4:00 PM Talk
Place: 725 Commonwealth Ave. CAS 502

Abstract:
Recent analysis of measurements returned by ionization gauges in the thermosphere are presented. These pressure sensors utilize modern electronics to provide good signal-to-noise ratios and have been used to reveal and understand thermospheric features using satellite- and rocket-based platforms. The presentation begins with an overview of the ionization technique and how it was employed on the Streak satellite. Analyses of the data returned by this instrument, called the IGS, from within the southern magnetospheric cusp and within the equatorial ionization anomaly are presented. These analyses give further understanding of the cusp upwelling phenomenon and the equatorial temperature and wind anomaly. Further analyses of data returned from a multiple-sensor ionization gauge carried into the lower thermosphere by a sounding rocket are also presented. The state of progress with utilizing these measurements to determine wind, temperature, and density profiles in the lower thermosphere is reported.

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CSP Seminar Speaker: Natchimuthuk Gopalswamy (NASA Goddard Space Flight Center)

April 11th, 2011 in In the News

Speaker: Natchimuthuk Gopalswamy
Affiliation: NASA Goddard Space Flight Center

Title: On interplanetary shocks driven by coronal mass ejections

Date: Thursday, April 14, 2011
Time: 3:30 PM Refreshments in CAS 500, 4:00 PM Talk
Place: 725 Commonwealth Ave. CAS 502

Abstract:
Traveling interplanetary (IP) shocks were first detected in the early 1960s, but their solar origin has been controversial. Early research focused on solar flares as the source of the shocks, but when CMEs were discovered, it became clear that fast CMEs are the shock drivers. Type radio II bursts are excellent signatures of shocks near the Sun (Type II radio bursts were known long before the detection of shocks and CMEs). The excellent correspondence between type II bursts and solar energetic particle (SEP) events made it clear that the same shock accelerates ions and electrons. Shocks near the Sun are also seen occasionally in white-light coronagraphic images. In the solar wind, shocks are observed as discontinuities in plasma parameters such as density and speed. Energetic storm particle events and sudden commencement of geomagnetic storm are also indicators of shocks arriving at Earth. After an overview on these shock signatures, I will summarize the results of a recent investigation of a large number of IP shocks. The study revealed that about 35% of IP shocks do not produce type II bursts (radio quiet) or SEPs. Comparing the RQ shocks with the radio loud (RL) ones revealed some interesting results: (1) There is no evidence for blast wave shocks. (2) A small fraction (20%) of RQ shocks is associated with ion enhancements at the shock when the shock passes the spacecraft. (3) The primary difference between the RQ and RL shocks can be traced to the different kinematic properties of the associated CMEs. On the other hand the shock properties measured at 1 AU are not too different for the RQ and RL cases. This can be attributed to the interaction with the IP medium, which seems to erase the difference between the shocks.

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CSP Seminar Speaker: Jeffrey J. Love (USGS)

March 23rd, 2011 in In the News

Speaker: Jeffrey J. Love
Affiliation: USGS Geomagnetism Program

Title: Movie-Maps of Low-Latitude Storm-Time Magnetic Disturbance

Date: Thursday, March 24, 2011
Time: 3:30 PM Refreshments in CAS 500, 4:00 PM Talk
Place: 725 Commonwealth Ave. CAS 502

Abstract:
Using data from a numerous magnetic observatories around the world, we examine movie-maps of low-latitude magnetic disturbance for several large magnetic storms. The principle disturbance pattern seen in the movie-maps, and also in statistical analyses of long time series, is the well-known (but seemingly insufficiently recognized!) dawn-dusk asymmetry. The disturbance at dawn (dusk) is about 20% higher (lower) than Dst, and this is often interpreted in terms of partial ring currents. However, an examination of magnetic-field data from mid-latitudes shows, very clearly, that the dawn-dusk asymmetry is more consistent with field-aligned currents (Birkeland) directed inwards at noon and outwards at midnight (Crooker and Siscoe 1981). Partial ring current might contribute to the ground magnetic disturbance, but its contribution to local-time disturbance morphology is very small.

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