Connect solar layers to seven instruments

The photosphere, chromosphere and corona are different regions of the Sun’s atmosphere. The photosphere supplies much of the visible light; the chromosphere lies above it, and the corona extends farther outward. Their radiation and plasma conditions differ, so one instrument cannot answer every question about them.

Aditya-L1 investigates questions including energy transfer, the hot corona, solar eruptions and the surrounding particle environment. An observing program needs to connect a scientific question to a measurable signal. A visually bright feature is not automatically the hottest feature, and brightness in different wavelength bands is not one universal thermometer.

The Visible Emission Line Coronagraph, VELC, observes the corona through imaging and spectroscopy. SUIT records solar images through ultraviolet filters. The Solar Low Energy X-ray Spectrometer, SoLEXS, and the High Energy L1 Orbiting X-ray Spectrometer, HEL1OS, examine different parts of the X-ray spectrum.

These are remote measurements: radiation reaches the observatory from the emitting region. Images can locate features, while spectra and time series characterize signals in other ways. Combining them requires attention to which region and time each measurement represents; a whole-Sun signal and a small image region do not have identical spatial scope.

Match the scientific question to the measured signal

The Aditya Solar wind Particle Experiment, ASPEX, and the Plasma Analyser Package for Aditya, PAPA, measure particles near the spacecraft. The magnetometer measures the local magnetic field. These in-situ measurements answer different questions from looking at photons arriving from the Sun.

Consider an original instrument-selection exercise. To study a bright ultraviolet patch on the solar disk, choose an imaging measurement such as SUIT. To investigate the local particle population and field carried past the spacecraft, choose the particle instruments and magnetometer. Both can help study an eruption, but they observe different physical signals at different locations.