Modal In Simple Present and Past Tenses

Modal Auxiliary Verb in Simple Present Tense

Verb Sentence
S + modal auxiliary + V bi + (rest of sentence)
Example:
We can go to the beach on time by bus.
We must go to the beach by bus.
We may go to the beach by bus.
We must can (X): We must be able to do all homeworks well.
Nominal Sentence
S + modal auxiliary + be + 3C
Example:
We can be there on time bu bus.
We must be there on time.
We may go be there on time.
We may can (X): We may be able to do all homeworks correctly.

Modal Auxiliary Verb in Simple Past Tense

Verb Sentence
S + modal auxiliary + V bi + (rest of sentence)
Example:
We could go to the beach on time by bus yesterday.
We had to go to the beach by bus.
We might go to beach by bus.
We had to can (X) : We had to be able to do all homeworks well.
Nominal Sentence
S + modal auxiliary + be + 3C
Example:
We could be there on time by bus last week.
We had to be there on time last week.
We might go be there on time.
We might can (X) : We might be able to do all homeworks correctly last week.

NASA Spacecraft Sees Solar Flare

On August 1st, the sun emitted a C-class solar flare that spawned what scientists call a coronal mass ejection, or CME, headed toward Earth. The CME impacted Earth's magnetic field August 3rd. CMEs occasionally hit Earth. This CME will have few noticeable consequences beyond producing an aurorae.

The CME hit Earth's magnetic field on August 3rd at 1740 UT. The impact sparked a G2-class geomagnetic storm that lasted nearly 12 hours--time enough for auroras to spread all the way from Europe to North America. The possible arrival of a second CME on August 4th might provide even better spectacular auroral displays.

CMEs are large clouds of charged particles that are ejected from the sun over the course of several hours and can carry up to ten billion tons of plasma. They expand away from the sun at speeds as high as a million miles an hour. A CME can make the 93-million-mile journey to Earth in just two to four days. Stronger solar storms could cause adverse impacts to space-based assets and technological infrastructure on Earth.

The sun goes through a regular activity cycle about 11 years long. The last solar maximum occurred in 2001 and its recent extreme solar minimum was particularly weak and long lasting. These kinds of eruptions are one of the first signs that the sun is waking up and heading toward another solar maximum expected in the 2013 time frame.

nasa.gov