The launch date for the two missions is no later than August 2022, the US space agency said in a statement on Friday.
One of the selected missions will study how the Sun drives particles and energy into the solar system and a second will study the Earth's response.
"These missions will do big science, but they're also special because they come in small packages, which means that we can launch them together and get more research for the price of a single launch," said Thomas Zurbuchen, Associate Administrator for the Science Mission Directorate at NASA headquarters in Washington.
The Sun generates a vast outpouring of solar particles known as the solar wind, which can create a dynamic system of radiation in space called space weather.
Near Earth, where such particles interact with our planet's magnetic field, the space weather system can lead to profound impact on human interests, such as astronauts' safety, radio communications, GPS signals and utility grids on the ground.
The more we understand what drives space weather and its interaction with the Earth and lunar systems, the more we can mitigate its effects - including safeguarding astronauts and technology crucial to NASA's Artemis programme to the Moon.
One of the two missions that NASA has selected is the Polarimeter to Unify the Corona and Heliosphere, or PUNCH. This mission will focus directly on the Sun's outer atmosphere, the corona, and how it generates the solar wind.
The second mission is Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites, or TRACERS. The TRACERS investigation was partially selected as a NASA-launched rideshare mission, meaning it will be launched as a secondary payload with PUNCH.
TRACERS will observe particles and fields at the Earth's northern magnetic cusp region - the region encircling the Earth's pole, where our planet's magnetic field lines curve down towards the Earth, NASA said.
( With inputs from IANS )