UFO's are real and fighting around the Earth!

I have an alien spacecraft in modern Earth's atmosphere, and rival alien spacecraft in Earth's Orbit. Both aliens are capable of maneuvering at great acceleration (100 G's?) equivalent to what is commonly portrayed for UFO's as seen in various videos in the atmosphere (and faster in space). They are aware if any kind of weapon is targeted at them with light speed, and are capable of accelerating any mass from subatomic particles up to a neutron star to near-light speeds in extremely short distances. Assume a spherical hull 100 feet in diameter with strength equivalent to battleship armor and near-infinite heat resistance.

The attackers in space are unwilling to cause massive collateral damage to the Earth (defined as any event causing the death of more than 1000 humans). With advanced notice, the defender aliens are willing to position themselves invisibly over urban centers to increase the odds of collateral damage.

**Given the limit of matter, but the choice of ANY matter from particle beams to neutronium slugs, and any velocity, can the aliens in orbit successfully target the aliens near the surface despite their early warning and great speed, or is the atmosphere too dense to allow projectile matter to enter fast enough without causing massive shockwaves or crust-damaging impacts from misses?**

The attacker entering the atmosphere more than superficially, or sending smart projectiles to pursue the near-surface craft, violate the limits of the question. They can carry or manufacture any exotic materials (like antimatter or exotic elements) on-board to use as projectiles or particle beams.

Bonus points if you can minimize the conflict being seen by humans and avoid any human casualties.