Low-altitude orbits of the microsatellites are mostly suitable for studying of the upper ionosphere dynamics. Here we present examples of the low- and mid-latitude ionosphere response to enhancements of the ionization caused by solar X-ray flares and solar energetic particles (SEP). Using ROCSAT-1 data we demonstrate that 1) at sunlit hemisphere the ion density at altitudes of ~600 km increases up to ~80% in response to flare-associated enhancements of the solar X-ray emission. 2) Ionospheric response to the SEP events is revealed both at sunlit and nightside hemispheres, where the ion density increases up to ~40% and 100%, respectively. 3) Direct ionization impact of the X-ray flares leads to increasing ionospheric conductivity and as result to intensification of the ionospheric current at low latitudes. The latter is revealed as a variation of the low-latitude geomagnetic field, so called Dst-variation. The presented examples indicate to importance of simultaneous measurements of the solar radiation (electromagnetic and particles) and key ionospheric parameters, such as ion density, temperature and velocity.