How do scientists monitor the Sun's activity?
Hello! I just want to humbly ask how do scientists and agencies like NASA, ESA, etc. monitor the activity of our Sun?
For example, if Solar storms are occurring in the Sun, how do we know it from Earth?
And another specific question:
We know that in about 5 billion years (is this correct?), the sun will end its main sequence phase and enter being a Red Giant, as it loses Hydrogen fuel in its core.
Hypothetically, should we (human civilizations) lived up to that era, how can we know that the Sun is losing hydrogen and enter its Red Giant phase? This is based on our present technologies and machines.
Thank you! Sorry for any wrong statements I may have made above, should there be any.