UPSC Prelims Practice Questions — VELC on board Aditya-L1 reveals asymmetric expansion of solar eruption that could impact space weather

Q1. With reference to a spacecraft placed in a halo orbit around the Sun–Earth L1 Lagrange point, consider the following statements: Which of the statements given above is/are correct?

  1. Since L1 lies between the Sun and the Earth, the spacecraft passes into the Earth's shadow once in every orbit and so loses its view of the Sun for a while.
  2. Although the spacecraft is closer to the Sun than the Earth is, it completes one revolution around the Sun in about the same time as the Earth does.
  3. The spacecraft can sample the solar wind before that wind reaches the Earth.
  • A. 1, 2 and 3
  • B. 1 and 3 only
  • C. 1 only
  • D. 2 and 3 only

Q2. Consider the following statements: Which of the following is correct in respect of the above statements?

  1. Direct measurements of the solar wind by a spacecraft at the Sun–Earth L1 point give only tens of minutes of warning before a disturbance reaches the Earth.
  2. The Sun–Earth L1 point lies only about 1.5 million km from the Earth, roughly one-hundredth of the Sun–Earth distance.
  • A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
  • B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
  • C. Statement-I is correct, but Statement-II is incorrect
  • D. Statement-I is incorrect, but Statement-II is correct

Q3. A spectrograph observing an erupting coronal feature in an emission line finds the line shifted to a shorter wavelength than its rest value. At the same time, an imager shows the same feature drifting northward across the sky. Which one of the following best describes the motion of the plasma?

  • A. It has a velocity component towards the observer and a northward component across the sky
  • B. It moves only northward across the sky, and the wavelength shift reflects heating of the plasma
  • C. It moves only towards the observer, and the northward drift seen is a projection artefact
  • D. It has a velocity component away from the observer and a northward component across the sky

Q4. With reference to coronagraphs and the solar corona, consider the following statements: Which of the statements given above is/are NOT correct?

  1. A coronagraph blocks the bright solar disc so that the much fainter surrounding corona can be observed.
  2. The corona appears far fainter than the solar disc because it is much cooler than the photosphere.
  3. Emission from highly ionised iron is used to trace coronal plasma because stripping many electrons from iron atoms requires temperatures of the order of a million kelvin.
  • A. 2 and 3 only
  • B. 2 only
  • C. 1, 2 and 3
  • D. 1 only

Q5. Why is observing the corona in a single narrow emission line, such as the green line of highly ionised iron, useful for studying how an eruption moves, compared with broadband white-light imaging alone?

  • A. An emission line is unaffected by plasma motion, so it shows the eruption's true outline
  • B. An emission line is formed in the photosphere, so it traces an eruption right down to its base
  • C. An emission line has a known rest wavelength, so any shift in it measures line-of-sight velocity
  • D. An emission line is brighter than the solar disc, so the instrument needs no occulting element

Q6. Consider the following statements regarding solar flares, coronal mass ejections (CMEs) and the solar wind: Which of the statements given above is/are correct?

  1. Radiation from a solar flare reaches the Earth within minutes, whereas the plasma of a CME typically takes one to several days.
  2. The solar wind is a continuous outflow of charged particles from the corona, whereas a CME is a discrete expulsion of plasma and magnetic field.
  3. A CME's arrival time at the Earth depends partly on the drag it experiences from the surrounding solar wind, so its shape can influence when it arrives.
  • A. 2 and 3 only
  • B. 1 and 2 only
  • C. 1 and 3 only
  • D. 1, 2 and 3

Q7. Consider the following assertion: Measuring the three-dimensional shape of a coronal mass ejection close to the Sun can improve forecasts of when it will reach the Earth. Which of the following statements support/supports the above assertion?

  1. A CME's shape governs how it interacts with the ambient solar wind and the drag it experiences on its way out.
  2. Widely used operational arrival-time models feed in a CME as a simple, symmetric cone.
  3. The temperature of a CME's plasma influences how strongly it disturbs the Earth's magnetic field.
  • A. 1 and 2 only
  • B. 1 only
  • C. 2 and 3 only
  • D. 1, 2 and 3

Q8. With reference to the effects of a strong geomagnetic storm triggered by a coronal mass ejection, consider the following statements: Which of the statements given above is/are correct?

  1. Heating of the upper atmosphere raises air density at low-orbit altitudes, increasing the drag on satellites there.
  2. Satellites in geosynchronous orbit are largely safe from storm effects because they orbit far above the layers of the atmosphere that cause drag.
  3. Currents in power-transmission lines during such storms arise because the CME's charged particles physically strike the lines on the ground.
  • A. 2 and 3 only
  • B. 1 and 3 only
  • C. 1 only
  • D. 1 and 2 only