(1) Perpendicular to surface of the earth
Denoting by B, BH and BV , the total feild of earth, horizontal component of earth’s field and vertical component of earth’s field, we have
BV = Bsin δ
where δ is the angle of dip.
At magnetic poles δ = 90° and hence BH = 0
At the poles, the earth’s totoal field is, therefore, the same as its vertical component. It is, therefore, perpendicular to the surface of earth at the poles.