# Surface area of the earth

## Homework Statement

Near Earth, the density of protons in the solar wind (a stream of particles from the Sun) is 8.60 cm-3 and their speed is about 490 km/s.
(a) Find the current density of these protons.
6.74E-7 A/m^2
(b) If Earth's magnetic field did not deflect the protons, what total current would Earth receive?

J=I/A

## The Attempt at a Solution

Using the equation above i used J*A=I, the problem is the area is used for the earth is apparently wrong(as i know my J is correct), so i looked online for it again and found 2 more answers(all the same numbers but to different powers of 10). Anyone know the actual surface area of the earth?(i would try plugging on all the ones i find but im limited on attempts for this question and i already used 2/5 of my tries)

ehild
Homework Helper
All those protons will reach the Earth which are in the beam of cross-section equal to that of the Earth.

ehild

What surface area do you need, the sphere or crossection?

What surface area do you need, the sphere or crossection?

id assume surface, what is corssection?

id assume surface, what is corssection?

There is the surface of the earth, which is somewhat a sphere or it's crossssection or the surface the electrons hit, so the area of a circle with the radius of earth. Which one have you been looking for and which one do you need?