Ionospheric disturbances during peak solar flares show dependence on flare energy

Study of Ionospheric disturbances over the Indian region during peak of a solar flares revealed significant correlation between change in total electron count and in X-ray energy from the sun for flares with higher electromagnetic energy whereas for flares with moderate and low electromagnetic energy no significant change was observed. Tracing these ionospheric disturbances are critical to understand radio wave propagation through the ionosphere which is a crucial part of radio communication.

Solar flares are an important element of Earth's Space Weather studies. Solar flares discharge an enormous amount of electromagnetic energy with peak flux in the Extreme Ultra Violet (EUV) and X-ray range of the electromagnetic spectrum. They are classified according to their strength. The smallest ones are B-class, followed by C, M and X, the largest. Each letter represents a ten-fold increase in energy output making X 10 times an M and 100 times a C.

Under normal conditions, the solar X-ray flux is too small to be a significant source of added additional ionization in the ionosphere. Hence during solar flare events, the total electron content (TEC) of the ionosphere increases causing disturbances in the ionosphere. This enhanced ionospheric electron density which is several folds greater than the background density is referred to as sudden increase of total electron content (SITEC).  The ionospheric remote sensing technique based on the Global Positioning System (GPS) derived total electron content (TEC) is a significant tool for supervising the electron density variation of the ionosphere.

Scientists from Doon University, Babasaheb Bhimrao Ambedkar University, Indian Institute of Tropical Meteorology, and Indian Institute of Geomagnetism, an autonomous institute of Department of Science and Technology (DST) investigated TEC during the peak of a solar cycle by scrutinising 450 solar flares of all classes -- five X-class solar flares, forty-nine M-class solar flares, and three hundred ninety-six C-class solar flares) for the year 2014. They found enhanced correlation between change in total electron count and change in X-ray energy from the sun (specially when solar flare location of flare on Sun surface was included) for X-class flares, whereas for M- and C-Class flares, no significant change was observed. The low equatorial latitude ionospheric response to solar flares was studied via GPS TEC signals from IGS station Bangalore, India.

The research published in the Journal of Advances in Space Research is one of the most comprehensive works from the Indian region in which 450 solar flares of all classes were scrutinized for the year 2014 which was the peak of the solar cycle 24. The results obtained can help to monitor and model space weather processes over the Indian region.

Publication link:

Contact Prof. Rajesh Singh, Email: rajesh[dot]singh[at]iigm[dot]res[dot]in

flare energy

Figure: Scatter plot shows X, M, and C-class solar flare correlation between ΔX-ray and ΔEUV Flux using ΔDVTEC adopting baseline (left panel) and mean (right panel) method approach. Correlation values are shown on the panels. The left column shows ΔX-ray flux and ΔDVTEC plots. Scatter diagrams of ΔEUV flux and ΔDVTEC can be seen in the right column.