K. S. Balasubramaniam

Helicity patterns on the sun

Abstract Solar magnetic fields exhibit hemispheric preference for negative (positive) helicity in northern (southern) hemisphere. The hemispheric helicity rule, however, is not very strong, — the patterns of mixed helicity were observed at different spatial scales in each hemisphere. Helicity patterns on scales larger than the size of typical active region were observed in distribution of active regions with abnormal (for a give hemisphere) helicity, in large-scale photospheric magnetic fields and coronal flux systems. We review the observations of large-scale patterns of helicity in solar atmosphere and their possible relationship with (sub-)photospheric processes.

SOLAR Hα OSCILLATIONS FROM INTENSITY AND DOPPLER OBSERVATIONS

Abstract : Chromospheric wave activity around flares and filaments has been a research focus for years, and could provide indirect measurements of local conditions that are not otherwise accessible. One interesting observed phenomenon is oscillations in filaments, activated by distant flares and the large-scale waves they produce. Characteristics of these oscillations, such as periods, amplitudes, and lifetimes, can provide unique information about the filament. We measure oscillation properties in flares and filaments from H chromospheric data using a new method that provides important spatial and frequency content of the dynamics. We apply the method to two flare events where filaments are observed to oscillate and determine their properties. We find strong oscillatory signal in flaring active regions in the chromosphere over a range of frequencies. Two filaments are found to oscillate without any detectable chromospheric wave acting as an activation mechanism. We find that filaments oscillate with periods of tens of minutes, but variations are significant at small spatial scales along the filamentary region. The results suggest that there is a frequency dependence of the oscillation amplitude, as well as a spatial dependence along single filaments that is more difficult to quantify. It also appears that the strength of the oscillations does not necessarily depend on the strength of the trigger, although there are other possible effects that make this conclusion preliminary. Applications of this technique to other events and different data sets will provide important new insights into the local energy densities and magnetic fields associated with dynamic chromospheric structures.

Estimate of Solar Maximum Using the 1-8 Å Geostationary Operational Environmental Satellites X-Ray Measurements

We present an alternate method of determining the progression of the solar cycle through an analysis of the solar X-ray background. Our results are based on the NOAA Geostationary Operational Environmental Satellites (GOES) X-ray data in the 1-8 \AA

CHROMOSPHERIC MASS MOTIONS AND INTRINSIC SUNSPOT ROTATIONS FOR NOAA ACTIVE REGIONS 10484, 10486, AND 10488 USING ISOON DATA

\,

Relationships Between Sequential Chromospheric Brightening and the Corona

band from 1986 - present, covering solar cycles 22, 23, and 24. The X-ray background level tracks the progression of the solar cycle through its maximum and minimum. Using the X-ray data, we can therefore make estimates of the solar cycle progression and date of solar maximum. Based upon our analysis, we conclude that the Sun reached its hemisphere-averaged maximum in Solar Cycle 24 in late 2013. This is within six months of the NOAA prediction of a maximum in Spring 2013.

High Resolution Solar Physics: Theory, Observations, and Techniques

This work utilizes Improved Solar Observing Optical Network continuum (630.2 nm) and Hα (656.2 nm) data to: (1) detect and measure intrinsic sunspot rotations occurring in the photosphere and chromosphere, (2) identify and measure chromospheric filament mass motions, and (3) assess any large-scale photospheric and chromospheric mass couplings. Significant results from 2003 October 27-29, using the techniques of Brown et al., indicate significant counter-rotation between the two large sunspots in NOAA AR 10486 on October 29, as well as discrete filament mass motions in NOAA AR 10484 on October 27 that appear to be associated with at least one C-class solar flare.

Solar drivers of the interplanetary and terrestrial disturbances

The chromosphere is a complex region that acts as an intermediary between the magnetic flux emergence in the photosphere and the magnetic features seen in the corona. Large eruptions in the chromosphere of flares and filaments are often accompanied by ejections of coronal mass off the sun. Several studies have observed fast-moving progressive trains of compact bright points (called Sequential Chromospheric Brightenings or SCBs) streaming away from chromospheric flares that also produce a coronal mass ejection (CME). In this work, we review studies of SCBs and search for commonalties between them. We place these findings into a larger context with contemporary chromospheric and coronal observations. SCBs are fleeting indicators of the solar atmospheric environment as it existed before their associated eruption. Since they appear at the very outset of a flare eruption, SCBs are good early indication of a CME measured in the chromosphere.