SOUTHERN MAINE ASTRONOMERS
Monthly meeting
Thursday, September 7, 2017
7:00 p.m.
at the Southworth Planetarium
Speaker:  Nishu Karna

Free and open to the public

From Ron Thompson, SMA President:

We have a guest Speaker this month, Nishu Karna, Ph.D. and she will be
discussing "Coronal Cavities on the Sun".

ABSTRACT: Coronal cavities are large-scale structures in the Sun's
corona that are closely related with the long-term evolution of the
magnetic field in the photosphere as well as associated with the
energetic solar activity such as prominence eruptions and coronal mass
ejections (CMEs). Coronal cavities are observed as elliptical-shaped,
relatively low density, dark regions above the solar limb in extreme
ultraviolet (EUV), Xray, and white-light coronal images. The locations
of cavities at high latitudes can be used to establish the time of
polar magnetic field reversal. Cavities are vital clues to the state
of the solar corona just prior to some CMEs and changes in the cavity
may trigger CMEs. The study of the properties of cavities from
formation to disruption will help us understand a CME&r squo;s
structure before it erupts and will also lead to improving predictions
of space weather effects.

BIO: Nishu Karna is a postdoctoral research fellow at
Harvard-Smithsonian Center for Astrophysics. Her research work focuses
on understanding the correlation between cavities, prominences, and
magnetic field topologies, by combining high-resolution space-based
observations with advanced Non Linear Force Free Field modeling. She
received her Ph.D. degree in Computational Sciences and Informatics
(Solar Physics) in May 2016 from George Mason University. During her
Ph.D. she worked on two solar topics: the first one was to measure the
areas of a polar coronal holes using Extreme Ultra Violet and magnetic
field synoptic maps for spanning two solar cycles (Solar Cycle 23 and
24). The second topic was her dissertation work on coronal cavities.
She made a comprehensive study of coronal cavities from May 2010 to
Feb 2015. The comprehensive study includes the development of cavities
detection tool, measurements of each cavity's structure (length,
width, height), the correlation between each cavity`s height, width
and length, cavities evolution with the solar cycle, and polar crown
cavities formation mechanism.

Hope to see you there.  Doors open at 6:30.

Ron

Ron Thompson
Southern Maine Astronomers