What is a solar flare?
A: A solar flare is an intense localized eruption of electromagnetic
radiation in the Sun's atmosphere.
Flares occur in active regions and are often, but not
always, accompanied by what?
A: Coronal mass ejections, solar particle events, and other solar phenomena.
Solar flares are thought to occur when stored
magnetic
energy in the Sun's atmosphere accelerates what?
A: Charged particles in the surrounding plasma.
Solar flares affect all layers of what?
A: The solar atmosphere (photosphere, chromosphere, and corona).
The plasma medium is heated to tens of millions of
kelvins, while electrons, protons, and heavier ions are accelerated to what?
A: To near the speed of light.
Flares produce electromagnetic radiation across the
electromagnetic spectrum at what wavelengths?
A: All wavelengths from radio waves to gamma rays.
Most of the energy is spread over frequencies outside
what?
A: Outside the visual range; most of the flares are not visible to the naked
eye and must be observed with special instruments.
Flares occur in active regions often around what?
A: Sunspots, where intense magnetic fields penetrate the photosphere to link
the corona to the solar interior.
Flares are powered by the sudden release of magnetic
energy stored in what?
A: The corona.
What are flare sprays?
A: They involve faster ejections of material than eruptive prominences and
reach velocities of 20 to 2000 kilometers per second.
The frequency of occurrence of solar flares varies with
what?
A: The 11-year solar cycle.
It can range from several per day during solar maximum
to how many during solar minimum?
A: Less than one every week.
The duration of a solar flare depends heavily on what?
A: The wavelength of the electromagnetic radiation used in its calculation.
This is due to different wavelengths being emitted
through different processes and at what?
A: Different heights in the Sun's atmosphere.
Solar flares lasting longer than approximately 30
minutes are regarded as what?
A: Long duration events (LDE).
It's not clear how the magnetic energy is transformed
into what?
A: The kinetic energy of the particles, nor is it known how some particles
can be accelerated to the GeV range (109 electron volt) and beyond.
X-ray and extreme ultraviolet radiation emitted by
solar flares are absorbed by what?
A: The daylight side of Earth's atmosphere and do not reach the Earth's
surface.
Therefore, solar flares pose no direct danger to whom?
A: Humans on Earth.
However, this absorption of high-energy
electromagnetic radiation can temporarily increase the ionization of the
upper atmosphere, which can interfere with what?
A: Short-wave radio communication and can temporarily heat and expand the
Earth's outer atmosphere.
This expansion can increase drag on satellites in low
Earth orbit, which can lead to what?
A: Orbital decay over time.
Flares produce radiation across the electromagnetic
spectrum, although with different what?
A: Intensity.
When were solar flares first observed by Richard
Carrington and Richard Hodgson independently?
A: On 1 September 1859 by projecting the image of the solar disk produced by
an optical telescope through a broad-band filter.
The most powerful flare ever observed is thought to be
the flare associated with what?
A: The 1859 Carrington Event.